linux-kernel - [PATCH] tracing: Update overrun counter when removing pages

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Message-Id: <1340998301-1715-1-git-send-email-vnagarnaik@google.com>
Date:	Fri, 29 Jun 2012 12:31:41 -0700
From:	Vaibhav Nagarnaik <vnagarnaik@...gle.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Justin Teravest <teravest@...gle.com>,
	David Sharp <dhsharp@...gle.com>, linux-kernel@...r.kernel.org,
	Vaibhav Nagarnaik <vnagarnaik@...gle.com>
Subject: [PATCH] tracing: Update overrun counter when removing pages

When removing pages from the ring buffer, its state is not reset. This
means that the counters need to be correctly updated to account for the
pages removed.

Update the overrun counter to reflect the removed events from the pages.

Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@...gle.com>
---
 kernel/trace/ring_buffer.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 96c2dd1..40862eb 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1346,10 +1346,9 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
 			 * If something was added to this page, it was full
 			 * since it is not the tail page. So we deduct the
 			 * bytes consumed in ring buffer from here.
-			 * No need to update overruns, since this page is
-			 * deleted from ring buffer and its entries are
-			 * already accounted for.
+			 * Increment overrun to account for the lost events.
 			 */
+			local_add(page_entries, &cpu_buffer->overrun);
 			local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
 		}
 
-- 
1.7.7.3

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